1. Field of Invention
The present disclosure relates generally to network systems. More particularly, the present disclosure relates to enabling a solid state relay arrangement to effectively replace multiple electromechanical relays in a wireline protection scheme.
2. Description of the Related Art
The demand for data communication services is growing at an explosive rate. Much of the increased demand is due to the fact that more residential and business computer users are becoming connected to the Internet. To address the demand for data communication services, the use of optical networks, such as a synchronous digital hierarchy (SDH) network or a synchronous optical network (SONET), is becoming more prevalent.
Within networks, line cards are typically used in multiservice platforms which provide electrical to optical interfaces. The line cards generally utilize telecom wireline applications or, more specifically, telecom wireline protection schemes. Telecom wireline protection schemes often utilize a series of double pole double throw (DPDT) electromechanical relays (EMRs) to provide varying equipment protection schemes.
FIG. 1 is a diagrammatic representation of a line card which utilizes a series of EMRs for an equipment protection scheme. A line card 100 includes a plurality of ports 124 which are each arranged to receive a single line from a multiplexing arrangement. By way of example, port 124a is coupled to a line 120 which is processed by a protection switching arrangement of DPDT EMRs 104a-f in a one-for-five protection scheme. Inputs 108, of which one may be considered to be working while five are protected, to EMRs 104a-c are selected by EMRs 104a-c such that output lines 112b-d of EMRs, along with a loopback line 112a, are passed into EMRs 104d, 104e. As will be appreciated by those skilled in the art, each EMR 104 is arranged to switch two input lines into a single output line. Each EMR 104d, 104e effectively switches a pair of lines 112 into single lines 116 which, in turn, are switched by EMR 104f into line 120 which is coupled to port 124a. 
Often, a line card may include a plurality of ports, each of which uses approximately N+1 DPDT EMRs, where “N” is a number of protected ports in a telecom protection scheme. Hence, the amount of space on a line card that is occupied by EMRs is often significant. Additionally, the physical size of each EMR is typically relatively large. In some instances, as for example in the case of relatively high density electrical line cards such as DS1, DS3, E1, ES, STM1E, and other line cards, it may not always be possible to fit all the EMRs needed to perform protection switching on the line cards due to space constraints. Since line cards and platforms on which the protection schemes are used are rapidly becoming denser in terms of the number of electrical ports supported on line cards and by platforms, the lack of available space on a line card for use in implementing protection schemes is becoming more prevalent, i.e., more design difficulties are arising when it comes to workable telecom wireline protection schemes which utilize multiple EMRs.
Further, since EMRs are typically relatively expensive, the use of multiple EMRs in a telecom wireline protection scheme on a line card may significantly impact the direct costs associated with the line card. Also, the reliability of EMRs is often questionable, e.g., EMRs are typically less reliable than other types of relays such as solid state relays. As such, the use of multiple EMRs may be impractical for at least the reasons that the amount of space needed on a line card in order to implement the EMRs is often substantial due to the size of the EMRs and the volume of EMRs, the cost of EMRs is relatively high, and the reliability of EMRs may be suspect.
Therefore, what is needed is a method and an apparatus which allows protection switching to be performed on telecom wires without requiring a significant amount of space on a line card. That is, what is desired is a system which effectively performs substantially the same function as multiple DPDT EMRs in a telecom wireline protection scheme on a line card, but occupies less space on a line card than the DPDT EMRs.